Black dyed interleaving paper



BLACK nYnn INTERLEAVING PAPER Ralph W. Peters and Joseph W. Mengel, Rochester, N. Y., assiguors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application October 1, 1952, Serial No. 312,634

5 Claims. (Cl. 92-3) This invention relates to a black dyed paper having particular utility in the packaging of light-sensitive photographic materials, and to a process of making the same.

In the packaging of certain light-sensitive photographic materials such as sheet film it is desirable to place what is known as interleaving paper between each sheet of film. Such paper should not transmit light and should have the quality of minimizing the accumulation and discharge of static electricity, that is it should have a very high electrical resistance (above eighty thousand ohms per square inch). paper is that it must be photographically inert, that is, its coloring material must not contain any substance such as sulfur which will tend to cause fogging or" the lightsensitive emulsion or other layer forming part of the photographic material with which the paper is used.

In the past considerable use has been made of a low electrical resistance paper containing carbon black as the coloring agent but such paper had the important disadvantage of causing smudging of whatever came into contact with it, for example the hands of the users of the film and the uniforms and gloves of the persons employed to package the film. This paper exhibited an undesirable degree of scufiing, causing rubbing ofi of carbon and paper dust, and resulting in a quality hazard for photographic goods. Despite these undesirable properties in the carbon black paper, no suitable replacement was known, although considerable etfort was expended in a search for such a paper.

We have now found that a black photographic packaging paper having the desired properties and particularly useful for interleaving purposes between sheet film, can be provided by a new process which includes the dyeing of the paper pulp with certain specific types of black dyes, such as duPont Fiber Black VF or Diamine Black Cap Extra Conc., preferably modified by a small amount of a yellow dye such as duPont Pontamine yellow SXPE. A dye such as Direct D Black EA Extra CF, Color Index No. 581 can be used without addition of yellow. All such dyes must be salt free. The making of the paper includes certain novel steps such as the maintaining of aluminum sulfate in the paper at a minimum amount so that the electrical resistance of the paper can be controlled at a figure above about 80,000 ohms per square inch. Beater time is minimized to lower the hydration of the pulp fiber and thereby to lessen cockle in the finished paper, which might in turn effect pressure desensitization of the film or other material with which the paper is used. Hydration is also minimized by using a so-called sharp equipment in the beater and Jordan to give a clean-cut fiber without fuzzing and opening of the fiber ends.

Accordingly it is an object of our invention to produce a black interleaving paper for use with light-sensitive materials, which paper combines the desirable properties of not transmitting light, having a high electrical resistance so as to minimize static, being free of sulfur-containing dyes and other materials which would be likely to cause fogging of the light-sensitive material, and being A third important property of such States Patent O ice free of any coloring materials which cause smudging. It is also an object of the invention to provide a method of producing such paper.

According to a preferred embodiment of the invention, which is given in an illustrative and not a limiting sense, we make up the new type of black interleaving paper by mixing ingredients as follows:

Per cent DuPont Fiber Black VF 4 /2 DuPont Pontamine Yellow SXPE /2 Aluminum sulfate 4 /2 Dry cornstarch (uncooked) 6 /2 High alpha, bleached sulfite Wood pulp 84 The makeup of this paper can also be expressed as follows:

2,000 pounds alpha pulp 150 pounds raw cornstarch 80 gallons alum (1.33 lbs/gal.)

108 pounds DuPont Fiber Black VF 12 pounds Pontamine Yellow SXPE 3,600 gallons water DuPont Fiber Black VF is salt free and is believed to be color index No. 581. This dye is believed to be:

Sodium salt of benzene-azo-3,6-disu1pho-8-amino-l-napthol-7-azo diphenyl-azo-m-phenylenediamine.

-S O sNa I DIIH2 Diamine Black Cap Extra Cone. (salt free) is the same formula dye.

The yellow dye is the sodium salt of dinitro azo distilbene tetra sulfonic acid, index No. 622, of the following structure:

NaOzS SOaNB 110.. '-NOZ N02 on mots SOsNa Both dyes are used in the concentrated salt free form.

A very desirable paper is obtained by using the black dye alone, but the use of the yellow dye has the important advantage of improving the appearance of the paper by reducing the somewhat blue-black appearance and rendering the paper a deeper black color.

The ingredients are mixed with water in the beater at F. for two hours at 6% consistency and are then put through a Jordan at 4% consistency. The mix then goes directly to the paper making machine Without any size being applied. It is important that the dyes used be salt free and that the aluminum sulfate content of the paper be controlled so" that the resistance of the finished paper can be controlled at a figure above 80,000 ohms per square inch.

In preparing the paper, the beater time is minimized to lower the hydration of the pulp fiber and thereby lessen cockle in the finished paper as such cockle might efiect pressure desensitization of the film or other light-sensitive material. So-called sharp equipment is used in the beater and Jordan to give a clean-cut fiber without fuzzing and opening of the fiber ends thus assisting in minimizing hydration.

The following examples also illustrate the invention:

Example II Using the Noble & Wood handsheet machine, handsheets were made from the following furnish:

2.42 grams DuPont Fiber Black VF 0.81 gram Pontarnine Yellow SXPE 1.0 liter of Soft Alpha pulp at 2.25% consistency, beat to a Williams slowness of 2025 seconds.

This paper gave excellent nonscuffing properties with a rich deep black.

Example III Using the Noble & Wood handsheet machine, handsheets were made from the following furnish:

2.42 grams Diamine Black Cap Extra Conc.

0.81 gram Pontamine Yellow SXPE 1.0 liter of Soft Alpha pulp at 2.25% consistency, beat to a Williams slowness of 20-25 seconds.

The following black dye can also be used, and yellow dye need not be used with this dye, even though it has a similar structure: Direct D Black EA Extra CF Color Index No. 581.

We claim:

1. A photographically inert, nonsmudging, nonlighttransmitting, nonpressure desensitizing black paper for use as interleaving paper in the packaging of light-sensitive photographic materials, said paper having an electrical resistance of over 80,000 ohms per square inch and containing a salt free black dye which is also free of any ingredients likely to cause fogging of light-sensitive material.

2. A black interleaving paper as set forth in claim 1 wherein the salt free black dye is selected from the group consisting of duPont Fiber Black VF, diamine Black Cap extra cone., and Direct D Black EA Extra CF.

3. A black interleaving paper according to claim 2 wherein the paper also includes a minor proportion of a yellow dye.

4. A black interleaving paper according to claim 3 wherein said yellow dye is duPont Pontamine Yellow, index No. 622.

5. A black interleaving paper as set forth in claim 1 having the following ingredients:

DuPont Fiber Black VF DuPont Pontamine Yellow SXPE Aluminum sulfate Dry cornstarch References Cited in the file of this patent UNITED STATES PATENTS 1,954,333 Sheppard Apr. 10, 1934 2,158,173 Baxter May 16, 1939 2,359,858 Iler Oct. 10, 1944 2,514,689 Woodward July 11, 1950 OTHER REFERENCES DuPont Tech. Bull., vol 6, No. 2, June 1950, pages 62 and 63. 

1. A PHOTOGRAPHICALLY INERT, NONSMUDGING, NONLIGHTTRANSMITING, NONPRESSURE DESENSITIZING BLACK PAPER FOR USE AS INTERLEAVING PAPER IN THE PACKAGING OF LIGHT-SENSITIVE PHOTOGRAPHIC MATERIALS, SAID PAPER HAVING AN ELECTRICAL RESISTANCE OF OVER 80,000 OHMS PER SQUARE INCH AND CONTAINING A SALT FREE BLACK DYE WHICH IS ALSO FREE OF ANY INGREDIENTS LIKELY TO CAUSE FOGGING OF LIGHT-SENSITIVE MATERIAL. 